This invention generally relates to digital data concentrators and more specifically, relates to a concentrator particularly suited for use in concentrating digital words representing samples of information transmitted over a telecommunication system.
Concentrators have been utilized in telecommunication systems to take advantage of the statistical probability that communication channels often only transmit information during a portion of the available transmission time. For example, a user may transmit data only in spurts such as a merchant requesting validation of a charge card before concluding a sale. Even the constant transmission of data at a relatively slow bit rate will appear as infrequent data from the perspective of a network element in which frames of data are handled at a rate much higher than the data bit rate. As long as such statistical probabilities are valid for a group of channels, the group of channels can be concentrated or coined onto a single transmission channel which is occupied substantially 100 percent of the time. Data words (samples) taken from the input channels of the group are packed onto the single channel.
A typical concentrator utilized in telecommunication systems combines a group of channels by first storing the digital words in each channel in a corresponding queue such as using a first in, first out buffer. The outputs of the buffers are connected to a selector which selects one of thee stored digital words during each clock cycle. Such an implementation requires independent FIFO buffers which are capable of operating at speeds sufficient to accommodate the storage and shifting of the digital words each clock cycle. Such memories are relatively expensive and require independent control. Thus, there exists a need for an improved concentrator which is more cost effective and eliminates the need for separate multiple word queues required to store the digital words associated with each communication channel.